1. Field of the Invention
Embodiments of the present invention generally relate to systems and methods for processing hydrocarbons. More particularly, embodiments of the present invention relate to systems and methods for regenerating spent catalyst.
2. Description of the Related Art
Fluid catalytic crackers (“FCC”) are a mainstay in the conversion of raw hydrocarbons into one or more products. An FCC consists of few components: one or more riser reactors, one or more disengagers, and one or more regenerators. A hydrocarbon feed and one or more catalysts are introduced to the riser reactor which is maintained at an elevated temperature and/or pressure. The cracking of the hydrocarbons within the riser reactor produces one or more cracked hydrocarbons and small quantities carbonaceous coke which is deposited on the surface of the catalyst. The coke includes mostly carbon, but also contains hydrogen, sulfur, nitrogen, and trace amounts of other elements. These coke deposits reduce the catalyst activity after passage through the riser reactor. The cracked hydrocarbons and the coked catalyst or (“spent catalyst”) exit the riser reactor and are introduced to one or more disengagers where the spent catalyst is separated from the cracked hydrocarbons. The cracked hydrocarbons are removed from the FCC for further processing and/or treatment. The spent catalyst is introduced to one or more regenerators where the coke is combusted, oxidized, and/or converted to one or more waste gases.
The combustion process removes coke from the surface of the catalyst, regenerating the catalyst, and permitting its recycle back to the riser reactor. However, the combustion process generates undesirable byproducts, such as nitrogen oxides (“NOx”), which must be removed or at least partially reduced to meet environmental regulations.
There is a need, therefore, for improved systems and methods for regenerating catalyst while producing less undesirable byproducts.